Surgical repair of rotator cuff injury is a common procedure, however structural failure of the surgical repair is a common complication of the surgery, and may be a frequent occurrence. There is therefore a recognized need to enhance the surgical repair of rotator cuff injuries. Recently, extracellular matrices have been used to aid surgical repair of connective tissues, although they have very modest mechanical properties and do not represent optimal designs of a product for their application. The objective of this program is to develop a product that has characteristics specifically designed to aid the surgical repair of rotator cuff injuries. A functional tissue engineering approach is being used to develop a device that will enhance the surgical repair of rotator cuff tendons. The device will be generated using the application of new technologies that have recently been developed at Synthasome, for which patent applications have been filed. The final product will be a device composed of a biomaterial with mechanical properties similar to native human rotator cuff tendon (designed to stabilize the repair site and confer mechanical functionality during the repair process), coated with a human extracellular matrix (to support in vivo biological repair). The overall long term hypothesis that this program will test is that a tissue engineered acellular construct composed of a functional scaffold and an extracellular matrix, designed to provide mechanical stability and functionality and support biologic repair, will enhance the quality of surgical repair for rotator cuff injury. The objectives of a previous Phase I application have been achieved. The objectives of this Phase II project are to determine the device effectiveness and safety in vivo (using a canine model of rotator cuff repair), and develop a human extracellular matrix-based repair product and test its safety in vivo (using a standardized biocompatibility model). Specific Aim 1. Determine effectiveness of the device in vivo, using a canine model of rotator cuff repair. Specific Aim 2. Prepare a human repair construct, and determine biocompatibility of the device. The successful outcome of these Aims will be the development of an acellular, human-based tissue engineered construct with the demonstrated ability to enhance the repair of rotator cuff injury, and with demonstrated safety. The successful outcome of this project will be the development of an acellular, human-based tissue engineered construct with the demonstrated safety and ability to enhance the repair of rotator cuff injury. The results obtained will provide the data necessary for a regulatory submission to the FDA to market the product. [unreadable] [unreadable] [unreadable]